The described invention belongs to the area of obstacle detection by an airborne platform.
The invention is more particularly aiming at the detection of ground obstacles. Ground obstacles are here defined as elevated obstacles supported from the ground, such as for example trees, buildings, high voltage wires fixed on pylons, or cable car wires in mountainous areas, and elevated terrain features such as mountains.
State of the art sensors for detecting obstacles comprise laser systems, millimetre wave radars, scanning radars and pulse radars.
Unfortunately, these sensors present severe performance limitations which restrain their operational use. For example, laser and millimetre wave radars suffer from poor visibility in bad weather, while scanning radar only allow achieving low update rate over wide fields of observation. Pulse radars are limited by detection problems at low altitude and short operational range, these limitations being constrained by the pulse length.
Document US2009/0174590 describes a radar system for aircraft which uses a FMCW (Frequency Modulated Continuous Form) signal for detecting presence of approaching airborne systems.
Unfortunately, this radar system is not suitable for detecting fixed low height obstacles from long range, for example obstacles at 15 meters height detected from 1000 meters distance.